Annual effective rate of interest

A bank offers the following certificates of deposit:

Term in years / Nominal annual interest rate compounded semi-annually

1 - 5%

2 - 6%

3 - 7%

4 - 8%

The bank does not permit early withdrawals. The certificates mature at the end of the term. During the next 6 years the bank will continue to offer these certificates of deposit. An investor initially deposits $10,000 in the bank and withdraws both principle and interest at the end of 6 years. Calculate the maximum annual effective rate of interest the investor can earn over the 6-year period. (The answer is given as 7.466%)

So I found the accumulated values for each to be, respectively: 10506.3 , 11225.1 , 12292.6 , 13685.7 ... but I'm not sure how to set it up to get the annual effective rates of interest.

Thank you!